Study of Mechanisms of Crystal Growth of Ferroelectric Polymers by Means of Measurement of Nonlinear Dielectric Spectrum

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Qualitative difference of ferroelectric polymers from ferroelectric ceramics is becoming clearer. Specifically, we observed remarkable polymer effects in phenomena such as formation and reversal of polarization, crystal growth, paraelectric-ferroelectric phase transition. Results of this study are summarized as follows.1) We succeeded in development of a new system to measure exactly and easily nonlinear properties such as electrostriction, second order and third order dielectric constants.2) We foud tha t a second order dielectric constant reflects a polarization state of crystals and a third order dielectric constant reflects the thermodynamical order of the Curite transision, The origin of piezoelectricity in VDF/TrFE copolymers was elucidated by an evaluation of an electrostriction constant.A theory of ferroelectric polymers was proposed. We found that the forroelectric properties of polymer crystals are affected by intermolecular interaction and intramolecular one and those competition.In addition to ferroelectric polymers including VDF, the ferroelectric properties of odd-number nylon were investigated. We found that its ferroelectricity is strongly affected by the hydrogen bonds.